Centrifugal separation



Nov. 15, 1955 Filed Feb. 3, 1951 L. P. sHARPLl-:s 2,723,799

CENTRIFUGAL SEPARATION 3 Sheets-Sheet l INVENTOR. LAURENCE P. SHARPLESATTORNEY Nov. 15, 1955 P. sHARPLEs CENTRIFUGAL SEPARATION 5 Sheets-Sheet2 Filed Feb. I5, 1951 INVENTOR. LAURENCE P. SHARPLES /wL/o G M ATTORNEYNov. 15, 1955 L.. P. SHARPLES 2,723,799

CENTRIFUGAL SEPARATION Filed Feb. 3 1951 5 Sheets-Sheet 3 INVENTOR.LAURENCE P. SHARPLES BY/J/Q G St/WMM ATTORNEY United States Patent OCENTRIFUGAL SEPARATION Laurence P. Sharples, Bryn Mawr, Pa., assignor toThe Sharples Corporation, a corporation of Delaware Application February3, 1951, Serial No. 209,218 Claims. (Cl. 233-20) This invention relatesgenerally to centrifuges and it relates particularly to centrifuges ofthe type designed to effect sedimentation or separation of solids fromliquids and the intermittent discharge of metered amounts of theseparated solids through the wall of the centrifugal rotor. Morespecifically, the invention relates to a centrifuge provided with one ormore solids discharge valves which are adapted to accumulate meteredamounts of solids which are discharged at suitably timed intervals.

For convenience the separated solids or high-density materials will bereferred to herein as sludge, and the lower-density materials will becalled the liquid, although it is to be understood that the liquid maybe separated by the centrifuge into various phases of differentdensities. Thus, the primary purpose of the centrifuge may be to removesludge from a liquid, or the removal of sludge may be incidental to thecentrifugal separation of the liquid into two or more phases. It hasheretofore been proposed to remove sludge from a rapidly rotatingcentrifuge rotor through a plurality of sludge valves spaced around theperiphery of the rotor, the inner surfaces of the rotor sloping towardthe valves in order that the sludge will be carried to the valves bycentrifugal force. Of course, the valves should not remain openunnecessarily, since it is desirable to minimize outward ow through themof substantial quantities of the liquid. It is thus desired to open thesludge valves at intervals for only suflicient time `for the sludgeaccumulation to pass through them. The opening of the sludge valves is amatter of considerable difficulty because of the high speed of rotationof the rotor in which they are located and the consequent largemechanical forces encountered. Electrically operated valves have notproven feasible because of the required slip rings and brushes operatingat speeds far above those commonly used in electrical equipment andbecause of the required location of such slip rings on rotating parts`where they may be subject to steam, other objectionable vapors, Water,and even to the sludge being separated in the rotor.

In prior valve constructions for removing separated sludge thepassageways for removing the sludge are usually small in size so thatthey tend to plug and thus become inoperative, Furthermore, thesepassageways and associated parts tend to wear on account of the highdischarge pressures of the sludge passing therethrough. In priorconstructions, furthermore, all the valves do not always have the samesensitivity. `Some valves for example in a given centrifuge may be moresluggish in opening and closing than others so that unequal amounts ofsludge pass out through the valves in the same centrifuge thus causingan unbalanced operation of the centrifuge.

It is also desirable that the rate of discharge of the sludge throughthe valves should be substantially equal to the rate of `separation ofthe sludge from the feed mixture passing through the centrifuge rotor.When using timed valves as now presently in use, it is sometimes dicultto properly adjust the rate of discharge ICC of the separated sludgefrom the rotor, so that it will equal the rate of separation of thesludge in the rotor. As a result, the rate of discharge of sludgethrough the valves is either too high or too low. In the former case,more or less lighter material is discharged from the rotor together withthe heavier separated material, and in the latter case, the amount ofseparated sludge gradually builds up in the rotor until it interfereswith the ei'liciency of the separation in the rotor, and also with theoperation of the valves.

According to the present invention there is provided a solids dischargevalve construction for a centrifugal clarifier or separator whichovercomes these disadvantages. The sludge valve comprises one or morechambers, which, when the valve is in the open position, lill withsludge material separated by the centrifugal rotor, and when the valveis in the closed position, permits a measured amount of the sludge todischarge from the rotor. The sludge valve is operated by any suitablemotor means, such as by a uid pressure actuated motor which is connectedto the valve for regulating intermittent discharge of the separatedsludge or sedimented solids through peripheral openings in the wall ofthe rotor, by alternately moving the valve into the open and closedpositions. The sludge valve proper comprises one or more chambers forreceiving the sludge which communicate with suitable inlet and outletpassageways or openings for the separated sludge. The sludge valve maybe provided with means, such as a stem, which is connected to a suitablemotor actuating means for moving the valve at predetermined timedintervals into open and closed positions. The relative dimensions of thesludge valve and associated parts are such that when the valve is in theopen position, the chambers therein communicate with the inside of therotor to permit the chambers to lill with separated sludge; and when thesludge valve is in the closed position, the chambers are in such aposition as to communicate with a zone outside the rotor and permit theaccumulated sludge contents from the sludge chambers to be discharged.

According to the present invention, metered or predetermined amounts ofseparated sludge are removed from the centrifuge at suitable timeintervals. The openings provided for removal of the sludge are fullyopened during the discharge cycle so that no clogging will occur. Thedischarge of sludge is fully controlled and is substantiallyuniform atall the valves. The centrifuge thus operates more uniformly in balanceand this balance is less upset when solids are removed than in priorconstructions. The sludge discharged by the present construction isgenerally also higher in solid content and the amount of liquiddischarged with the solids can be better controlled. There is alsoconsiderably less wear on the valve parts since the sludge is dischargedby the sludge valve without the hydraulic pressure from the interior ofthe centrifuge acting thereon, since the sludge chambers are not incommunication With the interior of the rotor at the time of dischargetherefrom. Also the balanced sensitivity of a plurality of motor meanswhen employed for simultaneously actuating a plurality of sludge valvesis not as important as in prior constructions since in the presentinvention these motor means, when used in plurality, operate to merelyactuate metering means. Therefore, the amount of sludge discharged ateach valve is not dependent upon the relation between the various valveoperating pressures and the resistance to motion of the various valves.

Further objects and advantages of the invention will be apparent fromthe following more detailed description thereof with reference to theaccompanying drawings, in which:

Figure 1 is a side` elevational view, partly in section,

of a centrifuge embodying the invention with portions thereof shownbroken away to disclose internal structure thereof;

Figure 2 is a horizontal sectional View taken just above the sludgevalves of Figure l with other parts omitted;

Figure 3 is an enlarged sectional view similar to Figure l, but withactuation mechanism of the sludge valve simplified and partlydiagrammatically shown in closed position;

Figure 3A is a fragmental view of the same sludge valve shown in Figure3 but shown in open position;

Figure 4 is an enlarged sectional view of the sludge valve assemblytaken on the line 4--4 of Figure 3;

Figure 5 is an enlarged plan view of the liquid feedcollar shown inFigure l;

Figure 6 is a fragmentary diagrammatic view of a timer-control of thesupply valve shown in Figure l; and

Figure 7 is a perspective view of a modified sludge valve construction.

Referring to the drawings, the invention in one form has been shown asapplied to a centrifuge 10 of the type shown in Patent 2,286,354. Therotor 11 is driven by a shaft 12, mounted for rotation within a support13, and itself driven by any suitable form of motor. The rotor 11 issecured to a sleeve 14 which is secured to and rotates with shaft 12.

As more fully explained in said patent, the mixture of liquids andsolids supplied through a feed or inlet pipe 15 ows downwardly throughthe space between tube 16 and sleeve 14 and outwardly below the skirt16a of tube 16. The easily separable solids move into the space orchamber 17 formed by the inclined walls 11a and 11b of the rotor 11.Eflicient separation or sedimentation of the remaining solids takesplace as liquid flows inwardly of the stratifying discs 18 and thesludge or heavier solid material flows outwardly therefrom. For purposesof clarity a limited number of discs 18 is shown, it being understoodthat a considerably larger number of discs in compact spacedrelationship would be normally employed as is well understood by personsskilled in the art. The liquid ows upwardly in the space adjacent theperiphery of the tube 16 and over a ring dam 19 for discharge by way ofstationary outlet 20.

Sludge collecting anywhere in the region of intersection of walls 11aand 11b is discharged into the sludge collecting chambers 5 provided inslidable cylindrical sludge discharge valves 6. A plurality, such aseight, equally spaced sludge discharge valves are positioned in circularopenings 9 provided in the wall of the rotor 11. The sludge dischargevalves 6 are dimensioned so as to slidably fit in the openings 9. Thesludge valves 6 are provided with a collecting chamber 5 of the samecapacity in which sludge is collected. The valves 6 are provided with ashoulder portion 6a adapted to seat against sealing gasket 2 positionedin a recess provided about openings 9. When the sludge discharge Valve 6is in the open position, as shown in Figure 3A, the sludge will bedischarged through passageways indicated by arrows 7 into the sludgechamber 5. At the same time the other end of valve 6 is in closedrelation to opening 9 in the rotor 11 so that no sludge in chamber 5 canpass out therefrom. When the sludge chamber 5 is filled with sludge, thesludge valve 6 is moved by suitable motor means, to be described later,to its closed position, as shown in Figure 3. The sludge accumulated inchamber 5 is then discharged through passageways, indicated by arrows 8,while the shoulder portion 6a of the other end of the valve 6 is sealedby gasket 2 against entry of any materials from the interior of thecentrifuge. The sludge discharged from the sludge chamber 5 is defiecteddownward by conical skirt or ring 22 and is discharged from a chute 23.The deliecting skirt 22 may be supported in any suitable way such as bybolts 22a extending through the stationary housing.

From the foregoing description of the sludge discharge CJI valves 6, itwill be understood that such valve in its function amounts to one ormore movable sludge collecting chambers which can be selectivelypositioned so as to communicate either with the interior of thecentrifugal rotor or bowl to collect the sludge separated at theperiphery of the rotor while being closed to communication with theexterior of the rotor, or the sludge collecting chambers can bepositioned so as not to communicate with the interior of the rotor, butcan communicate only with the exterior zone thereof. The passagewaysindicated by arrows 7 and 8 in Figures 3 and 3A can thus be consideredas openings communicating with the chamber 5 to provide the selectivecommunication of chamber 5 either with the interior or exterior of therotor as previously explained. When the rotor of the centrifuge isrotated in normal operation sludge valves 6 will be in the closedposition shown in Figure 3, the centrifugal force being sufficient tomaintain sludge valves 6 and the associated motor parts in closedposition.

A modified sludge valve construction is shown in Figure 7, wherein thesludge valve is formed from a hollow cylinder 60 closed at one end by aplate 61, and having a flange portion 60a at the other end adapted toengage gasket 2 about opening 9. Said other end of cylinder 60 isconnected to valve stem 24a of valve actuating motor 24. The cylinder isprovided with sludge inlet opening 62 and a sludge outlet opening 63.These openings are adapted to be closed or opened by the walls of theopenings 9 of the rotor depending upon the position of the valve inopening 9 of the rotor.

Associated with each of the slidable valves 6, eight of them being shownin Figure 2, is a sludge valve motor assembly 24. Each motor assembly 24has connected thereto a tube or pipe 25 forming a passageway in flowcommunication with an external source of an auxiliary liquid. In Figure1 the auxiliary liquid from a supply pipe 26, under control of amanually operable valve 27 of the fast opening and closing type, isdirected upwardly by a spray ring 28 into proximity with the overhanginglip 29a of a cup 29 secured to the rotor 11. The ring 28, a plan view ofwhich appears in Figure 5, is supported as by a bracket 23a secured tothe stationary support 13.

In accordance with the present invention, each of the sludge valves 6 isoperated into closed and open position as may be desired. Upon openingof valve 27 as by a lever 27a, the auxiliary liquid such as water isdirected through each of a plurality of openings 2Sb upwardly passed theinner edge of lip 29a and into the annular recess formed thereby, whichmay be best seen in Figure 3. With the aid of a plurality of fins 29h,the auxiliary liquid is quickly brought up to the speed of the rotor 11.The liquid flows upwardly through each iiow channel 3f) into one of theconnecting passageways or tubes 25.

Before valve 27 of Figure l is opened to admit the auxiliary liquid,centrifugal force, due to the high speed rotation of rotor 11, developedby motor valve stern 24a and piston 24b, Figure 3, is effective inmaintaining the valve stern 24a in the closed position, as shown inFigure 3. Valve stem 24a is connected to sludge valve 6 and is of suchlength as to permit sludge valve 6 to be in closed position as shown inFigure 3, thus permitting the sludge chambers 5 to communicate outsidethe rotor 11. Each motor valve-operating assembly 24 is supported bytube 25 brazed to the valve body and it is also supported from inclinedsurface 11b as by the angularly disposed surface 241 of the motor valvebody. The piston 24b is provided with a skirt, the inner finishedsurface of which slides in substantially liquid-tight engagement with apacking or piston ring 31 supported by the cylinder wall 32. Thediameter of piston 24b should be greater than the diameter of valve 6 inorder to permit piston 24b to move the valve 6 against the existinghydraulic pressure.

An orifice or leak-port 33 is provided in a flow channel or pipe 33adiagrammatically shown in Figure 3 as communicating with the pipe orpassageway 25.

With the above explanation of the functional relation of the parts inmind, it will now be assumed yvalve 27 is opened to admit auxiliaryliquid to the annular chamber formed by the skirt 29a. As the liquidcomes up to speed, it Hows upwardly through channel 30 of Figure 3 andoutwardly through-passageway 25 to the inner chamber 40 of the motorcylinder. Within a short interval of time, of the order of a tenth of asecond, the pressure head exerted by the liquid upon the inner face ofpiston 24b due to centrifugal force is adequate to move the piston 241)and connected valve stem 24a toward the axis of the rotor to the openposition, as shown in Figure 3A, to position sludge valve 6 in positionso as to permit separatedsludge to pass into chambers 5 through pathsindicated by arrows 7.

While the motor pistons are in open position, it will be understoodauxiliary liquid will be continuously discharged through orice 33, butsince the admission of liquid is at a rate materially greater than itsilow through orifice 33 the leak-port or orifice does not affect valveoperation. However, as soon as supply valve 27 is closed, the passageway25 is quickly emptied throughorifice or leak-port 33 and the motorcylinder moves to the closed position in a time interval of the order ofa tenth o f a second after closure of supply valve 27.

As ,shown in Figure 6, the supply valve 27 may be automatically openedand closed by a timing mechanism shown as including a solenoid 34 whoseenrgizationis under the control of a timer 35 of any suitable type ofwhich there are several readily available on the market andknown tothose skilled in the art. The timer 35 includes a knob 35a for adjustingthe on time of valve 27, that is,` the duration of the period duringwhich it is open, while a knob 35b adjusts the olf time or the periodduringtwhich the valve 27 is closed. Each period may be readilypredetermined by means of the index driven by each knob and theassociated scale, suitably calibrated as in minutes and seconds. Thusthe on and off times will be selected in conformity with therequirements of the required operation, whether the main function of thecentrifuge be the recovery of sludge present in large quantity, orwhether it be clarification of liquids containing only a small amount ofsludge, or otherwise. The flexibility and simplicity of the apparatusembodying the present invention-makes it particularly useful for a widevariety of applications.

In operation of the apparatus, feed mixture is introduced through feedinlet pipe 15 into the rotor 11, solids are separated therein andaccumulate in the region of the intersection of walls 11a and 11badjacent the openings 9 in the rotor wall. When the separated sludge listo be removed, valve 27 is turned on, as previously explained, to feedauxiliary liquid to the inner chamber of the motor cylinder. The sludgechambers 5 are then lled with sludge by action of centrifugal forcethereon. Inasmuch as the sludge chambers are preferably of the samecapacity, it will be obvious that predetermined or metered amounts ofsludge or of sludge plus liquid, will be removed from the rotor eachtime the sludge valves are moved into closed position. The timer may beset to operate at such a rate that the hourly capacity of the valvechambers will be somewhat greater than the amount of sludge to bedischarged per hour, thus assuring that all the sludge will becontinually evacuated from the rotor and with no more than apredetermined amount of additional liquids from the rotor. In order tomove sludge valves into closed position, the valve 27 is closedwhereupon pistons 24b are forced outward and away from the axis of therotor by the action of centrifugal force. The sludge valves 6 are thusmoved to their closed position, as shown in Figure 3, whereby the sludgein chambers 5 is discharged outside of the rotor. The sludge in chambers5 will be rapidly discharged due to the centrifugal force exertedthereon.

The features of the present invention pertain to a process and apparatusfor intermittently discharging from a centrifugal rotor a heavier phasesuch as sludge, and are 6 not limited to the particular steps,construction o`r details illustrated and described such as of feed ofthe mixture to the rotor or discharge of the subsided liquidconstituents separately from the rotor, or to the particularconstruction or type of centrifuges illustrated, or to the shape orconstruction of the valves or their operating means, or the like. Thusthe invention may be employed in connection with a centrifugal rotor ofthe so-called clarifier type, as illustrated in Figure 2, in which asolid constituent is'separated from only a single liquid, or may beemployed in connection with a rotor designed to separate two immiscibleliquids from each other during intermittent discharge of separatedsolids, or in connection with any other type of rotor, and irrespectiveof whether provided with a disc stack, wings, or otherwise.

While for convenience the invention has been more particularly describedin connection with the intermittent discharge of measured amounts ofsludge from a centrifugal rotor, it is to be understood that it isequally applicable to the intermittent discharge from the rotor ofmeasured amounts of separated heavy liquid phase, such as for examplesmall amounts of aqueous caustic soda which frequently accumulate in acentrifugal rotor as the heaviest phase in the centrifugal separation ofsoap stock from treated oil in the rening of vegetable oil, or forexample for the intermittent discharge of measured amounts ofaccumulated residual acid such as sulfuric acid in the centrifugalseparation of sludge from acid treated mineral oil in the refining ofthe latter. The invention is likewise applicable to operations wherein asingle liquid phase is clarified by the removal of residual amounts of asecond heavier liquid phase suspended therein, such as for example inthe separation of emulsions. While in the foregoing I have spoken of the`intermittent discharge of a heavy solid phase, or a heavy liquid phase,it is to `be understood that mixtures of the two are included, and thatin fact when a solid phase is intermittently discharged, it is normallyin a wet condition due to its contact with the liquid phase or phasesfrom which it has been separated.

The operation and advantages of the present invention will be apparentfrom the foregoing description. While preferred embodiments of theinvention have been described herein, it will `be understood thatchanges, omissions, additions, substitutions and/or modifications may bemade within the scope of the claims without departing from the spirit ofthe invention. Accordingly it is intended that the patent shall cover,by suitable expression in the claims, whatever features of patentablenovelty reside in the invention.

I claim:

1. A centrifuge comprising a rotor for effecting centrifugalsedimentation of ksolids from an admixture with liquid, a radiallymovable metering member disposed in and extending through the peripheralwall of said rotor, said metering member being closed to the exterior ofsaid rotor and opened to the interior of said rotor for measuringthereinto a quantity of said solids when said metering member is movedradially inward, said metering member being closed to the interior ofsaid rotor and opened to the exterior of said rotor for discharging saidmeasured quantity of said solids when said metering member is movedradially outward, and means for controlling the radial position of saidmetering member.

2. A centrifuge comprising a rotor for effecting centrifugalsedimentation of solids from an admixture with liquid, a plurality ofspaced discharge openings in the periphery of said rotor, a plurality ofradially movable solids discharge valves tted in said openings forcontrolling the discharge of separated solids through said dischargeopenings, each of said valves comprising a sludge accumulating chamber,means for moving said valves radially inward to selectively place eachof said sludge accumulating chambers substantially simultaneously incommunication with the interior of said rotor and to close said chambersagainst communication with the exterior of said rotor,

and means for moving said valves radially outward to close each of saidsludge accumulating chambers substantially simultaneously againstcommunication with the interior of said rotor and to place said chamberssubstantially simultaneously into communication with the exterior ofsaid rotor to discharge sludge accumulated therein.

3. A centrifuge as defined in claim 2 wherein each of the solidsdischarge valves are actuated in timed relation by motor means connectedthereto.

4. A centrifuge as dened in claim 2 wherein each of the solids dischargevalves is cylindrical in shape and provided with a chamber foraccumulating solids therein, each of said chambers being ofsubstantially the same capacity, and each said chamber extending to theperiphery of the cylindrical valve but spaced inwardly from each endthereof.

5. In a centrifugal separator adapted to effect centrifugalsedimentation of solids from an admixture with liquid and to eiiectperipheral discharge of said sedimented solids from the rotor of saidseparator, a discharge passage in the wall of said rotor, a solidsdischarge valve radially slidable in said discharge passage, saiddischarge valve comprising a sludge accumulating chamber havingpassageways adjacent each end thereof and spaced in relation to the wallof said rotor so that when the passageway nearest the axis of rotationof said rotor communicates with the interior of said rotor by movementof said valve radially inward the other opening is closed by the Wall ofsaid rotor and when the said other passageway communicates with theexterior of said rotor by movement of said valve radially outward theopening nearest the axis of rotation of said rotor is closed by the wallof said rotor, means for moving said solids discharge valve toward theaxis of rotation of said rotor until one of the passageways of saidchamber communicates with the interior of said rotor to accumulatesludge therein and means for moving said solids discharge valve awayfrom the axis of rotation of said rotor until the other passageway ofsaid chamber communicates with the exterior of said rotor to dischargeaccumulated solids therefrom.

6. The combination comprising a centrifugal rotor, means for rotatingsaid rotor, means for feeding into said rotor a mixture of immisciblephases to be separated including at least one liquid phase, means forremoving from said rotor adjacent the axis of rotation thereof at leastone liquid phase after its separation, means disposed about the innerperipheral wall of said rotor for accumulating a heavy phase, a radiallymovable metering member disposed in and extending through the peripheralwall of said rotor, said metering member being closed to the exterior ofsaid rotor and opened to the interior of said rotor for measuringthereinto a quantityof said heavy phase when said metering member ismoved radially inward, said metering member being closed to the interiorof said rotor and opened to the exterior of said rotor for dischargingsaid measured quantity of said heavy phase when said metering member is.moved radially outward, and means for establishing and disestablishingwithin said rotor a liquid column under centrifugal force for radiallymoving said metering member.

7. The apparatus of claim 6 wherein the means for radially moving themetering member is controlled exteriorly of said rotor.

8. The apparatus of claim 6 including a sealing member at the innerperiphery of said rotor for engagement by said metering member when thelatter is in radially outward position to seal the interior of saidrotor from the exterior thereof by centrifugal force.

9. A centrifuge having a rotor for effecting centrifugal separation ofphases, an opening extending through the peripheral wall of said rotor,a metering member disposed in said opening and radially movable therein,said metering member being closed to the exterior of said rotor andopened to the interior of said rotor for measuring thereunto a quantityof separated heavy phase when said metering member is moved radiallyinward, said metering member being closed to the interior of said rotorand opened to the exterior of said rotor for discharging said measuredquantity of said heavy phase when said metering member is moved radiallyoutward, and means for controlling the radial position of said meteringmember.

10. Apparatus in accordance with claim 9 having a plurality of saidmetering members substantially equally spaced about the circumference ofthe rotor, and means for radially moving said metering members.

References Cited in the tile of this patent UNITED STATES PATENTS1,321,353 Bacon Nov. 11, 1919 1,921,181 Fawcett Aug. 8, 1933 2,023,762Fawcett Dec. l0, 1935 2,200,202 Harvey May 7, 1940 2,286,354 FitzsimmonsJune 16, 1942 2,302,382 Scott Nov. 17, 1942 2,467,742 Hanno Apr. 19,1949 2,521,347 Davis Sept. 5, 1950 2,614,110 Davis Oct. 14, 1952 FOREIGNPATENTS 979,279 France Dec. 6, 1950

